The invention relates to a device for altering the compression ratio of an internal combustion engine.
A variable compression ratio unlocks consumption- and performance potential by adapting the same to the changing load on the internal combustion engine, wherein said potential remains untapped if there is a constant compression ratio.
By way of example, such an internal combustion engine is known from U.S. Pat. No. 1,115,477.
Also known is the use of an eccentric bearing shell in the large connecting rod eye to establish a variable compression ratio, wherein said bearing shell rotates in the same direction at half the rotation speed of the crankshaft. The compression ratio can then be adjusted by shifting the phase angle of the bearing shell.
On the website of the Gomecsys company, www.gomecsys.com, a device in this class is known which serves the purpose of altering the compression ratio of a four cylinder reciprocating internal combustion engine having a crankshaft drive. The crankshaft drive has a crankshaft which bears crankpins which are able to rotate on both ends and which each have a functional connection to one connecting rod and one piston arranged in a cylinder of the reciprocating internal combustion engine, said piston able to execute a sliding movement. In this way, the rotational movement of the crankshaft is converted into a bidirectional translational movement of the pistons in the cylinders with a defined stroke height. One eccentric is arranged between each crankpin and connecting rod eye of the connecting rods, said eccentric being able to rotate and having external gearing. By use of the eccentric, it is possible to adjust the height of the piston stroke and/or to alter the compression ratio. In this case, one first gear with outer toothing is included per eccentric, for the purpose of rotating the same, and is connected axially in a torque-proof manner to a second gear via a shaft which is oriented parallel to the crankshaft. This gear interacts with a gear having inner toothing, the same being rotated by a worm gear. As such, the compression ratio of the reciprocating internal combustion engine can be altered or adjusted by the rotation of the gear having inner toothing.
This design has the disadvantage of a substantial weakening of the load-bearing structure of the crankshaft, particularly in the crankshaft main bearing, resulting from the synchronization gearing which is required for the phase angle-/compression shift, from the crankcase to the eccentric bearing shell. This leads to a reduction of the increased power performance of the internal combustion engine which can be achieved with the compression ratio shift, and to an increase in friction loss resulting from the increased bearing diameter. As a result, a substantial amount of the potential which can be achieved by the variable compression ratio of the internal combustion engine is wasted.
The problem addressed by the present invention is that of avoiding the disadvantages named above.
According to the invention, a device (a synchronization gearing) is provided for the purpose of altering the compression ratio of a reciprocating internal combustion engine, which acts externally around the load-bearing crankshaft structures, and simultaneously ensures the required speed ratio. In this case, the gears (the third and fourth gears), the same being rotatably mounted in the crankcase, only move when the compression ratio is shifted, but not constantly as a result of the rotation of the crankshaft.
A device according to the present invention may include a crankshaft drive with a crankshaft with at least one crankpin mounted rotatably on both ends thereof, said crankpin having a functional connection with a connecting rod and a piston arranged in a cylinder of the reciprocating internal combustion engine in a manner allowing sliding movement, for the purpose of converting a rotational movement of the crankshaft into a bidirectional, translational movement of the piston with a defined stroke height, wherein a rotating eccentric with outer teeth is arranged between the crankpin and a connecting rod eye of the connecting rod, for the purpose of altering the stroke height of the piston, wherein a first gear with outer teeth is included for the purpose of rotating the eccentric, and is connected in a torque-proof manner axially to a second gear via a shaft arranged parallel to the crankshaft, said first gear is arranged on and intermeshing with a third gear which can be rotated by a control element, and the shaft is arranged parallel and radially distanced from the crankshaft suited for a single-cylinder reciprocating internal combustion engine.
A particularly preferred embodiment includes a fourth gear which is connected in a torque-proof manner to the third gear, wherein the fourth gear has a larger outer diameter than the third gear, and the fourth gear can be rotated by the control element.
An embodiment in which the crankshaft has a second crankpin which has a functional connection with a second connecting rod and a second piston, the same being arranged in a second cylinder of the reciprocating internal combustion engine in a manner allowing a sliding movement, for the purpose of converting the rotational movement of the crankshaft into a bidirectional, translational movement of the second piston with a defined stroke height, wherein a rotating second eccentric with outer teeth is arranged between the second crankpin and a connecting rod eye of the second connecting rod, for the purpose of altering the stroke height of the second piston, having a fifth gear with outer teeth is included for the purpose of rotating the second eccentric, and is connected in a torque-proof manner axially to a sixth gear via a second shaft arranged parallel to the crankshaft, the sixth gear having a functional connection with the eccentric having an outer toothing, makes it possible to use the device according to the invention in a multi-cylinder inline reciprocating internal combustion engine.
A further embodiment in which the second shaft is arranged in an axial borehole of the crankshaft, coaxially to the crankshaft has a particularly compact construction.
Embodiments of the present invention in which the third or the fourth gear can be rotated by the control element via a seventh gear or a gear rack, or a worm gear or a push actuator are particularly preferred.
Another embodiment in which an intermediate gear is arranged between the first gear and the fifth gear enables direct application of the fifth gear.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.